1. Field of the Invention
The present invention relates to a stackable module and a stack of modules for a processor system.
2. Description of the Related Art
The invention is particularly but not exclusively concerned with providing modules as an expansion system to allow new peripherals to be added to set top box motherboards. The intention is to provide modules that provide an expansion capability in a flexible and multi-functional fashion.
Existing set top box motherboards comprise an onboard processor which can implement a certain amount of functionality relating to data supplied via the set top box. It is increasingly the case that set top boxes need to be able to function with a variety of different peripherals, such as expanded memory, audio and video peripherals. Moreover, decryption of data is increasingly becoming necessary.
Thus, it is necessary for the motherboard to provide a number of different interfaces to support different peripherals, and also for the onboard processor to be able to take into account the extra functionality. This can lead to a motherboard that is complex and cumbersome, often unnecessarily so when such peripherals are not needed.
One way to resolve this difficulty is to provide a motherboard to which can be attached one or more expansion modules.
According to one aspect of the present invention there is provided a stackable module for a processor system, the module including: a support plate having a topside and an underside; a set of topside circuit components mounted on the topside of the support plate; a topside connector mounted to the topside of the support plate; an underside connector mounted to the underside of the support plate, wherein there are a first set of conductive tracks connected directly between the topside connector and the underside connector and a second set of conductive tracks connecting the topside connector to the topside circuit components, the underside connector and the topside connector being engageable with respective underside connectors and topside connectors of other modules, whereby the conductive tracks are arranged to convey transport stream data and transport stream control signals between modules in a stack.
The transport stream takes the form of digital, packetized, encoded data including audio and video data, for example in MPEG format. Information such as teletext, program guides, channel information, can also be provided. In addition, digital versions of analogue video and audio signals (not encoded) can be conveyed via the conductive tracks.
Another aspect of the invention provides a stack of modules in a processor system, the stack including: a main board having an interface connector and a set of main board components, the interface connector providing a set of pins for conveying transport stream data and transport stream control signals; at least one module comprising a support plate with an underside connector mounted to an underside of said support plate and a topside connector mounted to a topside of said support plate, the underside connector connected to the interface connector of the main board, wherein transport stream data and transport stream control signals are conveyed from at least some of said circuit components on the topside of the at least one module to the interface connector of the main board.
In a stack, the topside connector of a current module forms an UP port with the underside connector of the module above it. The underside connector of the current module forms a DOWN port with the topside connector of the module below it for the current module.
The topside and underside connectors can each comprise a set of pins for carrying memory access signals to allow a module to function as an external memory interface (EMI).
In the described embodiment the topside connector is a receptacle and the underside connector is a plug, but it will readily be appreciated that the reverse configuration is possible.
Each support plate can comprise at least one through-hole for receiving a support pillar. In such an arrangement, a support pillar can be provided on a support plate at a location so as to pass through a through-hole of an upper module in a module stack.
Each module can comprise a connector space-defining component which extends upwardly from the support plate by a distance calculated to define the minimum spacing between modules in a stack.
Modules of different types can be provided, and such modules can be stackable in a common stack.
According to one type, the circuit components of the module constitute a transport stream generating device that generates transport stream data and transport stream control signals. Examples are a tuner board or packet injector converter.
A second type of module has circuit components that constitute a device, which acts on transport stream data and transport stream control signals, for example a decryptor.
A third type of module has circuit components that constitute a device which does not utilize transport stream data and transport stream control signals, for example an EMI. In that case, the transport stream data and control signals are supplied via said topside and underside connectors directly to another module in the module stack.
A module can include a multiplexor for selectively selecting transport stream data from a lower module in the stack and an upper module in the stack (i.e., from the UP or DOWN port).
The stackable modules described herein provide expansion capabilities to set top box motherboards or main boards. In particular, transport streams are supported. The described embodiment supports memory access peripherals in addition to transport streams.
The modules can be stacked on top of each other to minimize main board requirements. The modules provide cableless expansion of general set top box peripherals.
Although the main application for the modules is considered to be for a set top box motherboard, they may be used in other applications.
The invention will now be described, by way of example only, with reference to the accompanying drawings.